Electric hammer



MayZO, 1941. J. a. cox 2,242,347

ELECTRIC HAMMER F iled Dec. 25, 1938 Bias Vo/fqge WITNESSES: INVENTOR @724 6? v I Joseph H. (0X BY Mam - ATTORNEY Patented May 20, 1941 ELECTRIC HAMVIER Joseph 11. Cox, Forest Hills, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsyl- Vania Application December 23, 1938, Serial No. 247,431

6 Claims.

" My invention relates to an electric hammer, and more specifically to an electrical systemfor eifecting reciprocation of an armature, which armature intermittently strikes a tool such as a hammer.

It is well known to provide a motor generator set to furnish alternating current and then to use rectifiers to pass alternate half cycles through each of a pair of hammer actuating coils. motor generator set can be replaced by a conventional electronic inverter. In the use of such electron inverter, however, it has been necessary to use a total of four rectifiers, two in the primary circuit as inverters, and two additional in the secondary circuit to control the impulses in the coils.

In accordance with my invention, two of the rectifiers have been eliminated together with the transformer, and the hammer actuating coils have been connected directly in the primary circuit instead of in the secondary circuit, as has been done previously.

' An object of my invention is to provide a simple electrical system involving a minimum number of electrical devices for operating .an electric hammer by a direct-current source of potential.

Another object of my invention is to provide an electrical system for operating a reciprocating tool, such as; for example, a hammer, which system is capableof handling high currents and transmitting a large energy impulse to a hammer.

Other objects and advantages will become more apparent from a study of the following specificatiou when considered in conjunction with the accompanying drawing, in which:

Figure 1 is a schematic diagram showing an electrical system'for operating a tool, such as, for example, a hammer, in accordance with my invention; and

Fig. 2 shows two-different wave forms for a controlling alternating-current source and the effect of a biasing voltage thereon.

Referring to Fig. 1. numerals i and 2 denote a pair of coils which are adaptedvto be alternately energized, thereby effecting reciprocation of an armature 3 which is located therebetween, the reciprocation of which armature eflect's intermittent striking of the tool 4, such as, for example, a hammer. The-positive terminal of the directcurrent source is connected by conductor 6 to one side of each of the coils. Coil l is connected in series with the direct-current source 5 and an electric discharge device of the immersed electrode type I. Coil 2 is connected'in series with direct-current source 5 and a second electric Such devices 1 and 8, respectively, comprise a vapor.-

izable conductive liquid, such as mercury, and have immersed therein a high resistance starting electrode l3 and i 4, respectively which is adapted to initiate a cathode spot and effect discharge of the discharge device. Connected in parallel with the discharge device 1 is a grid controlled thermionic type electric discharge tube l5, and connected in parallel with discharge device 8 is a similar grid controlled discharge tube 16. A single-phase a1ternating-current generator ll, which is represented by a rotor only, as shown in the drawing, the stator (not shown) being merely a permanent magnet, has a terminal I8 which is connected to grid i9 of tube 15 through a high resistance 26. Similarly, a terminal 2| is connected to grid 22 of tube I6 through a high resistance 23. The resistance may be of the order of 500,000 ohms, and the maximum voltage of alternating-current source I! may be of the'order of 50 volts depending upon the grid characteristics of tubes i5 and I6. Alternating-current generator i1 is driven by a direct-current motor 24 through a shaft 25, which motor has a suitable field 26 and a variable resistance 21 connected in series therewith, and which motor is energized by a direct-current source of potential, such as a battery 28. A biasing voltage is given to grids I9 and 22 by direct-current source 29 and adjustable resistor 30. The positive terminal of the directcurrent source 29 is connected through a portion of resistor 30 to the cathodes II and [2 of tubes I and 8, whereas the negative terminal is connected to the midpoint 3! of the coils of the alternating-current-generator il' through brush 32. The alternating-current generator ll may be of the type which produces a sine wave, as shown in Fig. 2, or may be an impulse generator producing a wave form such as shown in the lower part of Fig. 2. r I

Fig. 2 shows two different wave forms which may be desirable from alternating-current generator ll, namely, a sine wave and an impulse wave, as shown. The bias voltage furnished by battery 29 and resistor 30 and its relation to the wave form are also shown.

The operation of the device is as follows: Since grids i9 and 22 are connected to the exterior terminals of the alternating-current generator ll, they will be alternately impressed with a positive potential and when so impressed, they will effect a breakdown or discharge of the tube.

When tube I discharges, a direct-current path is completed from the positive terminal of the direct-current source 5 through coil I, conductor 33, discharge tube I5, ignition electrode I3 and cathode II of discharge device 1 to the negative terminal of direct-current source 5. The current passing through ignition electrode I3 and cathode efiects initiation of an arc and reduction of the resistance of the path between anode 9 and cathode I I to such an extent that a breakdown or discharge will occur between electrodes 9 and II, inasmuch as the direct-current source 5 constantly impresses a potential across electrodes 9 and II. Hence a large direct-current impulse will be conducted through coil I, thereby attracting armature 3 to the left. At the same time, commutating condenser 34, which is connected across coils I and 2, is charged by a relatively small current through coil 2, so that its positive terminal is next to tube 8. At the next half cycle of the alternating current, grid 22 becomes positive with respect to its cathode efl'ecting discharge of tube It and similarly of discharge device B. Hence the direct-current path is now established through the positive terminal of the direct-current source 5 through coil 2, discharge device 8 back to the negative terminal 01' source 5, and at the same time tubes I and 8 form a closed discharge path for commutating condenser 34. The condenser thus discharges ing said coil and eflecting reciprocation of said.

armature, said operating means including a separate electric discharge device having a relatively low current carrying capacity as compared to said first mentioned discharge device comprising an anode, a cathode and grid, an alternatingcurrent source having a terminal connected to said grid, said anode and cathode being connected in series with said coil and said directcurrent source so as to form a separate and substantially low current control path. 7

2. An electric hammer comprising, in combination, a direct-current source, a pair of coils, an armature therefor, a switching means connected in series with one of said coils and said directcurrent source, a second switching means connected in series with the other of said coils and said direct-current source, each of said switching from the anode III to cathode I2 of tube 8, and

thence through tube 1 in a direction opposite to the previous current flow therethrough, thus aiding in deionizing tube I. At this time both tube 1 and auxiliary tube I5 are extinguished and do not restrike, inasmuch as a suitable positive potential is no longer impressed on grid I9, and both main tube I and auxiliary tube I5 have become deionized by the commutating effect of condenser 34 thereon. Hence a large direct current is passed through coil 2, thus attracting armature 2 to the right and causing it to strike against tool or hammer 4. This alternate energiaation oi coils I and 2 is continuous; hence a reciprocating motion oi armature 3 will be ef- Iected which will cause an intermittent striking of the tool or hammer l. I

In view oi the large current capacity of discharge devices I and 8, it will be seen that an armature 3 will strike tool or hammer 4 with a tremendous force, thereby making it suitable for heavy duty work. Obviously, in accordance with the broader aspects of my-invention, any grid controlled thermionic tubes having suflicient current carrying capacity may be substituted for the immersed ignition electrode type of tubes 1 and 8.

Further, by suitably adjusting the speed of motor 24 and thus the frequency of the alternator II, the number of hammer impacts per minute may be controlled at will. The adjust- 'ment is, most desirably, so made that the magnitude of impact and number of impacts per minute is just of the right value for most efficient operation.

1 am, of course,, aware that others particularly after having had the benefit of the teachings of my'invention may devise other circuits embodying my invention for operating an electric hammer, and I, therefore, do not wish to be limited to the specific showings made in the drawing and he descriptive disclosure hereinbefore made, but

means comprising electric discharge devices liaving relatively high current carrying capacity and operating means which opens said first switching means while closing the second, then opens said second switching means while closing the first, in periodic succession, thereby periodically energizing said first coil and said second coil in succession and effecting reciprocation of said armature, said operating means including a separate pair of grid controlled electric discharge devices of relatively low current carrying capacity as compared to said first mentioned discharge device, one for each of said coils thereby forming a low current carrying control path, and an alternating-current source having a terminal connected to one of said grids and another terminal connected to the other of said grids.

3. An electric hammer comprising, in combination, a direct-current source, a pair of coils, an armature therefor, a switching means connected in series with one of said coils and said directcurrent source, a second switching means connected in series with the other of said coils and said direct-current source, each of said switching means comprising an electric discharge device I the first, in periodic succession, thereby perihaving relatively high current carrying capacity and operating means which opens said first switching means while closing the second, then opens said second switching means while closing first mentioned discharge devices, each comprising an anode, cathode and a grid, the anode and cathode of one of said electric discharge devices being connected in series with said direct-current source and one of said coils, the anode and cathode of the other of said electric discharge de- 'vices being connected in series with said other coil and said direct-current source, said grids being connected to opposite terminals of said alwish to be limited only by the scope of the 941- t rna ing-current source.

4. An operating device for an electric hammer comprising, in combination, an inverter devoid a transformer and including .a direct-current source, a pair of highly inductive coils, an armature therefor, two electric discharge devices of the immersed ignition electrode type having relatively high current carrying capacities, each connected in series with one of said coils and said direct-current source, operating means which alternately effects discharge of said electric dis- 'iirst-named discharge devices alternately.

5. An operating device for an electric hammer 1y low current carrying capacities, each comprising an anode, cathode and a grid, the anode-and cathode of one of said electric dis charge devices being connected in series with said direct-current source and one of said coils, the anode and cathode of the other ofsaid electric discharge devices being connected in series with said other coil and said direct-current source, said grids being connected to opposite terminals 01 said alternating-current source and a condenser connected across said coils which aids in deionizing said first-named discharge devices alternately.

6. An operating device for an electric hammer comprising, in combination, an inverter devoid comprising an inverter devoid of a transformer,

.which-includes, in combination, an inverter deof the immersed ignition electrode type and having relatively high current carrying capacities,

eachconnectedinserieswithoneofsaidcoils and said direct-current source. operating means "which alternately eifects discharge of said electric discharge devices thereby alternately energisingsaidcoilsandeifectingreciprocaticnof said armature, said operating means including alas reciprocation of said armature.

pa'irofelectricdischargedevieeshaving relativea transformer and including a direct-current source, a pair of highly inductive coils, an arms.- ture therefor, a condenser connected across said coils to efl'ect commutation therebetween, two electric discharge devices of the immersed ignition electrode type and having relatively high current carrying capacities, each connected in series with one of said coils and said direct-current source. a pair of grid controlled electric discharge devices having relatively low current carrying capacities, each connected in parallel with one of said immersed electrode type discharge devices, an alternating-current source having terminals connected to said grids thereby alternately impressing a positive potential on said grids to effect alternate ignition of said grid controlled electric discharge devices which in turn effects alternate ignition of said immersed electrode type electric discharge devices thereby eflecting alternate energization of-said coils and Joann n: cox. 

